(1) Field of the Invention
This invention relates to Read Only Memory manufacturing techniques more particularly to a method of producing high density Read Only Memory devices by making self-aligned and closely spaced polysilicon lines.
(2) Description of Related Art
Semiconductor memories have been one of the fastest growing segments of the semiconductor industry. As the density of the memory cells has increased, the cost of the devices has decreased, resulting in more and more applications.
As each new generation of memories has evolved, the chip density has roughly quadrupled. This density increase has been achieved by new and innovative cell design. Current techniques are crowding the capabilities of optical technology for alignment of masks, exposure of photoresist with light limits, and the effects of substrate surface planarity on resist exposure.
The double polysilicon read only memory (ROM) process is a known process in the art, such as shown by Y. Naruke in U.S. Pat. No. 5,002,896. However, the use of spin-on-glass in such processes is unknown.
Researchers in the integrated circuit field do use spin-on-glass plus etchback processes as shown by Chu et al U.S. Pat. No. 4,775,550; Merenda et al U.S. Pat. No. 4,826,786; Batty U.S. Pat. No. 4,894,351; and Malazgirt et al U.S. Pat. No. 4,986,878.